Wavelength tunable semiconductor lasers are key components in many technological systems, exemplarily WDM optical fiber communication systems, and such lasers are known. For instance, P. R. Berger et al., Applied Physics Letters, Vol. 59, p. 117 (1991) discloses a surface emitting laser (SEL) that utilizes the Peltier effect of the substrate to achieve thermally induced tuning. However, this effect allows only a relatively small tuning range (typically about 1 nm). A semiconductor laser having much larger (e.g., &gt;10 nm) tuning range would be of significant technological interest.
Electro-optic tuning of lasers by means that comprise liquid crystal material is known. However, the prior art devices typically involve an external cavity, with a separate liquid crystal-containing element in the external cavity. See, for instance, J. R. Andrews, IEEE Photonics Technology Letters, Vol. 2(5), p. 334; H. Tsuda et al., IEEE Photonics Technology Letters, Vol. 3(6), p. 504; H. Tsuda et al., Applied Physics Letters, Vol. 61(17), p. 2006; and Qi Zhang et al., Optics Letters, Vol. 17(1), p. 43. Such light sources typically comprise a multiplicity of components in addition to the laser diode and thus typically would be inconvenient to use. This application inter alia discloses a simple, compact, wavelength-tunable semiconductor laser having a relatively large tuning range.